Length grading machines, or grain separators, are typically used to separate a stream of grain containing various types and sizes of grain into its constituent parts, for example, wheat, durum, oats, barley and rice, and/or to separate such grains from other seed contaminants. These machines employ a rotating member, or cylinder, which is mounted in an interior space of a housing of the grain separator, and which includes lifting pockets, or indentations, located along an interior surface thereof. As the cylinder rotates, the indentations, according to their size, receive and lift particular lengths, or sizes, of granules out of a stream of grain and drop the granules into a trough that is mounted within the cylinder. The stream of grain is fed into the rotating cylinder by a spout, which extends through a sidewall of the housing and through an end piece of the indented cylinder. To prevent grain from leaking out, at an interface between the spout and the rotating cylinder, a seal is typically mounted about the spout so as to interface with an external surface of the cylinder end piece.